This invention relates to a belt-drive method and apparatus, and, more specifically, it relates to a method and apparatus for use in a situation where power is transmitted via a belt from a drive shaft to a driven shaft having rotational inertia, and is accompanied by minute fluctuations in the instantaneous angular velocity.
In instances where an internal combustion engine is used as a drive and this drive force is transmitted to a driven shaft via a belt, the internal combustion engine generates a drive force only during the power or combustion stroke and does not generate the drive force during any other engine stroke. There is a recurring fluctuation in the instantaneous angular velocity of the rotating drive shaft and consequently there is the problem that, as the load on the driven shaft increases, the influence of the fluctuation in the angular velocity becomes more apparent.
For this reason, a flywheel is provided on the crankshaft of the typical internal combustion engine in order to increase the force of inertia and thereby achieve smoother running. However, the twisting strength of the crankshaft places limitations on how far the force of inertia can be increased, thus making it impossible to avoid the occurrence of fluctuations in the angular velocity of the crankshaft (drive shaft) of approximately 1.5.about.2.0 degrees or less in a gasoline internal combustion engine and of approximately 6.about.8 degrees or less in a diesel internal combustion engine.
Therefore, for a belt-drive device which uses an internal combustion engine as a power source, the fluctuation in the angular velocity simultaneously also causes the peripheral velocity of the belt to fluctuate, and, in cases where the rotational inertia of the driven shaft is large, slippage between the pulley of the driven shaft and the belt will result from the fluctuation in the peripheral velocity. This in turn causes a considerable reduction in the life of the belt.
For example, in an automobile, although the generator is driven using the internal combustion engine as a power source, because the generator shaft has a large amount of rotational inertia, the fluctuations in the engine angular velocity as described above cause the belt to constantly slip on the pulley of the generator shaft. Even if it is but a minute amount each time, this slipping results in various problems such as wear of the contact surfaces and the generation of frictional heat and noise. Moreover, because, with respect to the drive shaft, the generator has a speed-increasing speed ratio relationship using a small-diameter pulley, the above problems become even more noticeable.
Especially with V-ribbed belts, which are used more and more for the purpose of reducing the amount of space required, because wear of the belt surface is a direct cause of significant shortening of the life of the belt, the slippage is a problem which cannot be overlooked.
In order to solve this problem, various measures have heretofore been implemented to improve the structure or strength of the belt, and these measures have achieved a certain amount of success. Nevertheless, so long as fluctuations in the angular velocity of the drive shaft cannot be avoided, these measures will continue to fall short of a complete solution, and can do no more than reduce the wear of the belt and the generation of noise to a certain extent.
This invention provides new means to, when power is transmitted via a belt between a drive accompanied by minute fluctuations in the angular velocity and a driven shaft having rotational inertia, as in the case of an internal combustion engine, completely eliminate the shortening of the life of said belt resulting from the minute fluctuations in the angular velocity, and thus greatly increase the life of the belt.